I have my Rachael hooked up to a CSP2+ and run the Rachael's volume wide open. Tonight I noticed a hum from speakers, which went away as soon as I dropped the attenuator on the Rachael down 2 notches. Again, this is no big deal -- and remedied by this slight adjustment -- but does anyone have a guess as to why it would only/what causes hum when wide open?Scott

all (4) +/-speaker terminals and the - RCA short to the IEC ground and each other?

steve pinged me that "The resistance of the output transformer secondaries is less than 1 ohm, so many meters would read that as a short when in reality it is not. I don't think there is anything wrong with your amp or safety issues that should prevent you from continuing to use it and trace down the noise problem."

I have run into what seems to be somewhat of a common problem. I am getting some pretty noticeable hum. I only have two sources coming from my Decware input selector box into the amp. One is a Denon turntable and the other is an Oppo 105 BDP. When I remove the interconnects from the Oppo the hum is eliminated. All of my components are run through a low dollar surge protector which is going into a standard wall socket. I have tried switching plugs around. Moving the Oppo/Amp off of the surge protector individually and plugging them directly into the wall with no change in the hum (didn't really expect to make a difference). I don't have the budget to have a special circuit created just for this room or the buy any exotic type of power conditioner. Any suggestions as to a reasonable remedy would be welcomed. I have a Rachel amp and have read in the forum that their may be a difference in the grounding on these compared to other Decware amps. I am no engineer and don't know if this actually accurate just trying to get it quiet. I have also noticed that dvd soundtracks do not play as loud as music cd's. Having to turn up the volume to play some concert dvd's just makes the humming a larger problem. I spoke to Steve about this issue and he has sent me some 6N2P input tubes to bump up the gain.

I'm wondering if you have more of a ground loop issue. You are using 94db/w speakers?

I've told Steve that while I'd like to get rid of the remaining hum, it is very quiet, and comparing to a SS Bel Canto amp...MUCH quieter! There is no PSU hash or tweeter hiss, nothing spurious, just very low-level hum. I'm close to forgetting about it until I test out my Mini-Torii which should be here soon.

I'm troubleshooting some other electrical issues in the house regarding DC current.